Image display apparatus

ABSTRACT

An image display apparatus according to an embodiment of the present technology includes an optical modulator, an optical device, and a sensor unit. The optical device splits a modulated light beam modulated by the optical modulator into a first split light beam and a second split light beam, the first split light beam and the second split light beam each travelling in a different direction, and prevents a light beam, which backwardly travels on an optical path of the first split light beam and enters the optical device, from travelling along an optical path of the second split light beam. The sensor unit is disposed on the optical path of the second split light beam and detects a state of the second split light beam.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. application Ser. No.16/628,227, filed Jan. 2, 2020, which is a National Stage ofInternational Application No. PCT/JP2018/019073, filed May 17, 2018,which claims the benefit Japanese Application No. 2017-136618 filed Jul.12, 2017, the entire contents of each of which are hereby incorporatedby reference herein in their entirety.

TECHNICAL FIELD

The present technology relates to an image display apparatus such as aprojector.

BACKGROUND ART

Conventionally, image display apparatuses such as a projector have beenwidely used. For example, an optical modulator such as a liquid-crystaldevice modulates a light beam from a light source and the modulatedlight beam is projected to a screen or the like for displaying an image.A mercury lamp, a xenon lamp, a light emitting diode (LED), a laserdiode (LD), or the like is used as the light source. A solid-state lightsource which is the LED, the LD, or the like among them has longlifetime, and lamp replacement is not required unlike the conventionalone. Moreover, such a solid-state light source has an advantage that thelight is turned on immediately after it is powered on.

Patent Literature 1 has described an image projection apparatus thatdisplays a 3D (stereoscopic) picture by making use of a difference inpolarized light characteristics. In this image projection apparatus, aright-eye picture is made incident upon a prism-type beam splitter tobecome a P-polarized light beam and a left-eye picture is made incidentupon the prism-type beam splitter to become an S-polarized light beam.The prism-type beam splitter combines the right-eye picture with theleft-eye picture. The combined picture is projected to a screen via aprojection lens (Paragraphs [0040], [0049], and [0051] of specification,FIG. 3 , and the like of Patent Literature 1).

Patent Literature 2 has described a projection-type display apparatusincluding a polarization beam splitter that reflects respective RGBlight beams to a reflective type light bulb and transmits the lightbeams modulated by the reflective type light bulb toward the projectionlens. In this projection-type display apparatus, an area sensor isdisposed on a surface of the surfaces of the polarization beam splitter,on an opposite side of a surface that the respective RGB light beamsenter. The area sensor detects a state of leaking light that has notbeen reflected by the polarization beam splitter and has passed throughthe polarization beam splitter as it is. The respective components canbe easily aligned on the basis of a detection result of the area sensor.Moreover, a degradation state of each component can be grasped(Paragraphs [0044] to [0058] and [0083] of specification, FIG. 3 , andthe like of Patent Literature 2).

CITATION LIST Patent Literature

Patent Literature 1: WO 2014/132675

Patent Literature 2: Japanese Patent Application Laid-open No.2008-129261

DISCLOSURE OF INVENTION Technical Problem

It can be considered that various projectors such as a large projectorfor digital cinema using a laser light source and a projector configuredfor 3D pictures will be propagated in the future. In such an imagedisplay apparatus such a projector, it is desirable to provide atechnology that enables a state of a light beam to be detected with highaccuracy.

In view of the above-mentioned circumstances, it is an object of thepresent technology to provide an image display apparatus capable ofdetecting a state of a light beam with high accuracy.

Solution to Problem

In order to accomplish the above-mentioned object, an image displayapparatus according to an embodiment of the present technology includesan optical modulator, an optical device, and a sensor unit.

The optical device splits a modulated light beam modulated by theoptical modulator into a first split light beam and a second split lightbeam, the first split light beam and the second split light beam eachtravelling in a different direction, and prevents a light beam, whichbackwardly travels on an optical path of the first split light beam andenters the optical device, from travelling along an optical path of thesecond split light beam.

The sensor unit is disposed on the optical path of the second splitlight beam and detects a state of the second split light beam.

In this image display apparatus, the optical device splits the modulatedlight beam into the first and second split light beams. Further, theoptical device prevents the light beam, which backwardly travels on theoptical path of the first split light beam and enters the opticaldevice, from travelling along the optical path of the second split lightbeam. Therefore, a state of the modulated light beam can be detectedwith high accuracy by arranging the sensor unit on the optical path ofthe second split light beam.

The optical device may be disposed on a main optical path of themodulated light beam, emit the first split light beam along the mainoptical path, and emit the second split light beam along another opticalpath.

The optical device may include a first emitting surface that emits thefirst split light beam, and a second emitting surface that emits asecond split light beam, the second emitting in surface being differentfrom the first emitting surface. In this case, the sensor unit may bedisposed on a side of the second emitting surface.

The optical device may include a light-splitting surface that isdisposed obliquely to a direction of incidence of the modulated lightbeam that enters the optical device.

The light-splitting surface may transmit a part of the modulated lightbeam that enters the light-splitting surface as the first split lightbeam, and reflect another part of the modulated light beam as the secondsplit light beam. In this case, the sensor unit may be disposed on aside of the light-splitting surface that reflects the second split lightbeam.

The light-splitting surface may reflect a part of the modulated lightbeam that enters the light-splitting surface as the first split lightbeam, and transmit another part of the modulated light beam as thesecond split light beam. In this case, the sensor unit may be disposedon a side of a surface on an opposite side of the light-splittingsurface.

The optical device may split the modulated light beam such that anamount of light of the first split light beam is larger than an amountof light of the second split light beam.

The image display apparatus may further include: a combining unit thatcombines a plurality of modulated light beams to generate a combinedmodulated light beam; and a projecting unit that projects the combinedmodulated light beam generated by the combining unit. In this case, theoptical device may be disposed between the combining unit and theprojecting unit, and split the combined modulated light beam into thefirst split light beam and the second split light beam.

The optical device may include a light-splitting prism including a firstsurface that the modulated light beam enters, a light-splitting surfacethat splits the modulated light beam that enters the first surface, anda second surface from which the second split light beam split by thelight-splitting surface is emitted. In this case, the sensor unit may bedisposed in proximity to the second surface of the light-splittingprism.

The optical device may include a polarization beam splitter, a halfmirror, or a glass plate.

The image display apparatus may further include a first emitter thatemits a first image light beam in a first polarization state in a firstdirection. In this case, the optical device may include alight-splitting surface that is disposed obliquely to the firstdirection. Further, the light-splitting surface may transmit a part ofthe first image light beam to travel on a first optical path extendingin the first direction, and reflect another part of the first imagelight beam to travel on a second optical path extending in a seconddirection substantially orthogonal to the first direction. Further, thesensor unit may be disposed on the second optical path.

The image display apparatus may further include a second emitter thatemits a second image light beam in a second polarization state in thesecond direction. In this case, the light-splitting surface may bedisposed obliquely to the second direction, reflect a part of the secondimage light beam to travel on the first optical path, and transmitanother part of the second image light beam to travel on the secondoptical path.

The sensor unit may include a first filter that extracts a light beam inthe first polarization state, a first sensor that detects a state of thelight beam extracted by the first filter, a second filter that extractsa light beam in the second polarization state, and a second sensor thatdetects a state of the light beam extracted by the second filter.

The sensor unit may detect at least one of intensity, chromaticity, or aluminous flux shape of the second split light beam.

The optical device may be configured for applying a predetermined actionto an incident light beam, and split the modulated light beam thatenters the optical device into the first split light beam to which thepredetermined action is applied and the second split light beam to whichthe predetermined action is not applied.

Advantageous Effects of Invention

As described above, in accordance with the present technology, the stateof the light beam can be detected with high accuracy. It should be notedthat the effects described here are not necessarily limitative and anyeffect described in the present disclosure may be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A schematic diagram showing a configuration example of an imagedisplay apparatus according to an embodiment of the present technology.

FIG. 2 A schematic diagram showing a configuration example of an imagegenerator.

FIG. 3 An enlarged diagram showing a portion of an image combining unitin an enlarged state.

FIG. 4 An enlarged diagram showing the portion of the image combiningunit in the enlarged state.

FIG. 5 A schematic diagram showing a configuration example of a sensorunit.

FIG. 6 schematic diagram showing a configuration example of the sensorunit.

FIG. 7 A schematic view showing another configuration example of thesensor unit.

FIG. 8 A schematic diagram showing a configuration example of an imagedisplay apparatus shown as an comparative example.

FIG. 9 A schematic diagram showing another configuration example of theimage generator.

FIG. 10 A schematic diagram showing another configuration example of theimage generator.

FIG. 11 A schematic diagram showing another configuration example of theimage generator.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments according to the present technology will bedescribed with reference to the drawings.

Image Display Apparatus

FIG. 1 is a schematic diagram showing a configuration example of animage display apparatus according to an embodiment of the presenttechnology. An image display apparatus 500 is a cinema projector using alaser light source and is capable of displaying a 3D (stereoscopic)picture by utilizing polarized light characteristics of light.

Hereinafter, for the sake of convenience, as the image display apparatus500 is viewed from above, a description will be made assuming that the Xdirection in the figure is left and right directions, the Y direction isa depth direction, and the Z direction is a height direction. As amatter of course, the respective directions of XYZ are not limited tothose directions and the image display apparatus 500 can be used inarbitrary direction and orientation.

The image display apparatus 500 includes a first image generator 100, asecond image generator 200, an image combining unit 50, a half-waveplate 60, a projection optical system 70, a sensor unit 80, and acontrol unit 90.

The first image generator 100 generates and emits a first image lightbeam 10 that constitutes a right-eye image in a 3D picture. The firstimage generator 100 modulates a light beam for each of a red light beam,a green light beam, and a blue light beam (respective RGB color lightbeams) and combines the modulated light beams of the respective colors.In this manner, the first image generator 100 generates the first imagelight beam 10. It should be noted that the modulated light beams of therespective colors are also a concept included in an image light beam.

As shown in FIG. 1 , the first image generator 100 emits the first imagelight beam 10 to the left in the X direction. Further, the first imagegenerator 100 emits the first image light beam 10 as being a P-polarizedlight beam with respect to the junction surface 51 of the imagecombining unit 50.

In this embodiment, the first image generator 100 corresponds to a firstemitter. Further, the X direction corresponds to a first direction.Further, the state of being a P—polarized light beam with respect to thejunction surface 51 corresponds to a first polarization state.

The second image generator 200 emits a second image light beam 20 thatconstitutes a left eye image in the 3D picture. The second imagegenerator 200 modulates a light beam for each of respective RGB colorlight beams and combines the modulated light beams of the respectivecolors to thereby generate the second image light beam 20.

As shown in FIG. 1 , the second image generator 200 emits the secondimage light beam 20 to the front (in the figure, downwards) in the Ydirection. Further, the second image generator 200 emits the secondimage light beam 20 as being a P-polarized light beam with respect tothe junction surface 51 of the image combining unit 50.

The first and second image generators 100 and 200 have substantially thesame configuration. In FIG. 1 , some components are schematically shownregarding each of the first and second image generators 100 and 200.Each of the first and second image generators 100 and 200 will bedescribed later in detail.

The half-wave plate 60 is disposed between the second image generator200 and the image combining unit 50. The half-wave plate 60 has afunction of rotating the polarization direction by 90 degrees over theentire wavelength band of the three primary colors of light to be used.A specific configuration of the half-wave plate 60 is not limited andmay be arbitrarily designed.

The half-wave plate 60 rotates the polarization direction of the secondimage light beam 20 emitted from the second image generator 200 by 90degrees. Therefore, the second image light beam 20 as being anS-polarized light beam with respect to the junction surface 51 isemitted by the image combining unit 50.

In this embodiment, the second image generator 200 and the half-waveplate 60 correspond to a second emitter. Further, the Y directioncorresponds to a second direction substantially orthogonal to the firstdirection. Further, the state of being an S-polarized light beam withrespect to the junction surface 51 corresponds to a second polarizationstate.

The image combining unit 50 is a prism-type beam splitter. The imagecombining unit 50 has characteristics of a polarization beam splitterhaving high reflectance with respect to an S-polarized light beam andhaving high transmittance with respect to a P-polarized light beam overthe entire wavelength range of the three primary colors of light to beused.

In this embodiment, two right-angled isosceles prisms of substantiallythe same type are joined and a polarization film having predeterminedoptical characteristics on the junction surface 51 is formed. Thejunction surface 51 is disposed at an angle of 45 degrees with respectto a travelling direction of each of the first image light beam 10 andthe second image light beam 20 and these S-polarized light beam andP-polarized light beam with respect to the junction surface 51 aredefined.

The junction surface 51 transmits the first image light beam 10 which isa P-polarized light beam and reflects the second image light beam 20which is an S-polarized light beam. Accordingly, the first and secondimage light beams 10 and 20 are combined and are emitted toward theprojection optical system 70. Therefore, in this embodiment, theright-eye image is displayed by the first image light beam 10 whichbecomes a P-polarized light beam with respect to the junction surface 51and the left eye image is displayed by the second image light beam 20which is an S-polarized light beam.

In this embodiment, the image combining unit 50 corresponds to anoptical device. This point will be described later in detail.

The projection optical system 70 is disposed on an emitter side of theimage combining unit 50. The first and second image light beams 10 and20 combined by the image combining unit 50 are enlarged at apredetermined scale magnification and are projected to a projectingobject such as a screen. Accordingly, the right-eye image and theleft-surface image are displayed. The projection optical system 70includes a plurality of projection lenses and the like, for example. Aspecific configuration of the projection optical system 70 may bedesigned as appropriate.

The sensor unit 80 includes a sensor 81 that receives light and iscapable of detecting a state of a light beam. The state of the lightbeam includes, for example, luminance (intensity), chromaticity, aluminous flux shape, and the like. It should be noted that the luminousflux shape is a concept including the size (cross-sectional area) of theluminous flux.

An arbitrary luminance sensor, a chromaticity sensor, or the like may beused as the sensor 81. Further, an image sensor such as an array sensor,a CMOS sensor, and a CCD sensor constituted by a plurality of sensorsmay be used as the sensor 81.

As shown in FIG. 1 , the sensor 81 is disposed in proximity to a surfaceon a front side (in the figure, lower side) of the image combining unit50. The sensor 81 enables a state of each of the first and second imagelight beams 10 and 20 to be detected with high accuracy. This point willbe described later in detail.

The control unit 90 controls the operations of the respective mechanismsin the image display apparatus 500. The control unit 90 is electricallyconnected to the first and second image generators 100 and 200, theprojection optical system 70, and the other mechanisms and outputs acontrol signal to the respective mechanisms. For example, the operationsof the light source section and the optical modulator included in thefirst and second image generators 100 and 200 can be controlled.

The control unit 90 includes, for example, a CPU, a RAM, a ROM, and thelike. The CPU loads a control program recorded in the ROM in advanceinto the RAM and executes the control program. In this manner, therespective mechanisms are controlled. The configuration of the controlunit 90 is not limited and arbitrary hardware and software may be used.For example, devices including a programmable logic device (PLD) of afield programmable gate array (FPGA) or the like, an applicationspecific integrated circuit (ASIC), and the like may be used. Further,although the control unit 90 is shown by the broken line in FIG. 1 , theposition at which the control unit 90 is disposed and the like are alsonot limited and may be set as appropriate.

Image Generator

FIG. 2 is a schematic diagram showing a configuration example of theimage generator. FIG. 2 shows a configuration example of the first imagegenerator 100 in a case where the image display apparatus 500 shown inFIG. 1 is viewed from the front side in the Y direction. The half-waveplate 60 and the second image generator 200 shown in FIG. 1 are locatedon a deep side of the image combining unit 50 shown in FIG. 2 and theillustration is omitted.

The first image generator 100 includes a light source section 101, anillumination optical system 110, and an image modulating unit 130. Thelight source section 101 generates a white light beam W and emits thegenerated white light beam W to the illumination optical system 110. Asolid-state light source such as a light emitting diode (LED) and alaser diode (LD), a mercury lamp, a xenon lamp, or the like is disposedat the light source section 101, for example.

For example, a solid-state RGB light source capable of emitting each oflight beams of the respective RGB colors may be used, those emittedlight beams may be combined, and the white light beam W may begenerated. Alternatively, a solid-state light source that emits light inthe blue wavelength range and fluorescent phosphor that is excited by ablue light beam and emits a yellow light beam may be disposed. In thiscase, the blue light beam and yellow light beam are combined and thewhite light beam W is emitted.

The illumination optical system 110 includes an integrator device 111,polarization converters 112, 113, and 114, a light collection lens 115,a cross-dichroic mirror 116, reflection mirrors 117 and 118, a dichroicmirror 119, and relay lenses 120, 121, and 122.

The integrator device 111 includes first and second fly eye lenses 111 aand 111 b. The white light beam W passes through those first and secondfly eye lenses 111 a and 111 b. In this manner, nonuniformity ofluminance of the white light beam W is lowered.

The polarization converter 112 has a function of adjusting thepolarization state of the white light beam W that enters it via theintegrator device 111. An arbitrary optical device such as apolarization plate and a polarization beam splitter may be used as thepolarization converter 112. The white light beam W passing through thepolarization converter 112 is emitted to the cross-dichroic mirror 116via the light collection lens 115.

The cross-dichroic mirror 116 splits the white light beam W emitted fromthe light collection lens 115 into a red light beam R having a longerwavelength and a green light beam G and a blue light beam B having ashorter wavelength. The red light beam R split by the cross-dichroicmirror 116 is reflected by the reflection mirror 117 and enters thepolarization converter 113. The red light beam R whose polarizationstate has been adjusted by the polarization converter 113 is emitted tothe image modulating unit 130 via the relay lens 120.

The green light beam G and the blue light beam B split by thecross-dichroic mirror 116 is reflected by the reflection mirror 118 andenters a polarization converter 114. The green light beam G and the bluelight beam B whose polarization state has been adjusted by thepolarization converter 114 are split by the dichroic mirror 119 into thegreen light beam G having the longer wavelength and the blue light beamB having the shorter wavelength.

The green light beam G split by the dichroic mirror 119 is emitted tothe image modulating unit 130 via the relay lens 121. The blue lightbeam B split by the dichroic mirror 119 is emitted to the imagemodulating unit 130 via the relay lens 122.

The image modulating unit 130 includes reflective polarizers 131 (131R,131G, and 131B), reflective optical modulators 132 (132R, 132G, and132B), wave plates 133 (133R, 133G, and 133B), polarization beamsplitters 134 (134R, 134G, and 134B), and half-wave plates 135 (135R,135G, and 135B) which are disposed for the respective RGB colors.Further, the image modulating unit 130 includes a color combining prism136 and a polarization plate 137 for generating the first image lightbeam 10.

The reflective polarizers 131 are prism-type beam splitters. Therespective RGB light beams are emitted from the respective relay lenses120 to 122 shown in FIG. 2 as being an S-polarized light beam withrespect to the junction surface of the reflective polarizers 131.

The reflective polarizer 131R reflects an S-polarized component of thered light beam R toward the wave plate 133R. The wave plate 133Rfunctions as a compensation plate that compensates for black leveldegradation, rotates the polarization direction of the incident redlight beam R, and emits it to the reflective optical modulator 132R. Theangle of rotation of the polarization direction is set as appropriatesuch that a high-accuracy image is projected.

The reflective optical modulator 132R modulates and reflects theincident red light beam Ron the basis of an image signal correspondingto the red light beam R supplied from outside. Although a reflectivetype liquid-crystal panel is typically used as the reflective opticalmodulator 132R, the present technology is not limited thereto.

The red light beam R modulated by the reflective optical modulator 132R(referred to as a modulated light beam R with the same reference sign)enters the reflective polarizer 131R via the wave plate 133R. AP-polarized light beam component of the modulated light beam R passesthrough the junction surface and enters the polarization beam splitter134R.

The polarization beam splitter 134R functions as a polarizationconverter. With this polarization beam splitter 134R, the polarizationstate of the modulated light beam R is adjusted and unnecessary light iscut. The polarization direction of the modulated light beam R emittedfrom the polarization beam splitter 134R is rotated by the half-waveplate 135R by 90 degrees and is emitted to the color combining prism136.

The green light beam G and the blue light beam B are similarly modulatedby the reflective optical modulators 132G and 132B and are emitted tothe color combining prism 136 from the reflective polarizers 131G and131B via the half-wave plates 135G and 135B.

The color combining prism 136 is configured by joining a plurality ofglass prisms (four right-angled isosceles prisms of substantially thesame type), for example. On the junction surface of each of the glassprisms, two interference films having predetermined opticalcharacteristics are formed.

A first interference film among them reflects the blue light beam B andtransmits the red light beam R and the green light beam G. A secondinterference film reflects the red light beam R and transmits the bluelight beam B and the green light beam G. The first and secondinterference films have characteristics having high reflectance withrespect to an S-polarized light beam and having low reflectance withrespect to a P-polarized light beam.

In this embodiment, the polarization direction of each of the modulatedlight beams RGB is rotated by the half-wave plates 135 by 90 degrees.Accordingly, each of the to modulated light beams RGB is made incidentas an S-polarized light beam with respect to the junction surface of thecolor combining prism 136. As a result, a high-luminance image can beprojected.

The modulated light beams R and B are reflected by the junction surfaceand the modulated light beam G passes through the junction surface.Accordingly, the modulated light beams RGB are combined on the sameoptical path and the first image light beam 10 is generated. Thepolarization direction of the first image light beam 10 is adjusted bythe polarization plate 137 and it is emitted to the image combining unit50.

It should be noted that in this embodiment, the direction of the firstimage generator 100 is set as appropriate such that a light beam whichis an S-polarized light beam with respect to the junction surface of thecolor combining prism 136 becomes a P-polarized light beam with respectto the junction surface 51 of the image combining unit 50. Therefore,the first image light beam 10 which is a P-polarized light beam withrespect to the junction surface 51 of the image combining unit 50 isemitted from the first image generator 100.

As described above, the second image generator 200 has substantially thesame configuration as the first image generator 100. The second imagegenerator 200 emits the second image light beam 20 which is aP-polarized light beam with respect to the junction surface 51 of theimage combining unit 50. The half-wave plate 60 rotates the polarizationdirection of the second image light beam 20 by 90 degrees. Accordingly,the second image light beam 20 which is an S-polarized light beam withrespect to the junction surface 51 is emitted to the image combiningunit 50.

It should be noted that in FIG. 1 , the reflective polarizer 131R, thereflective optical modulator 132G, the wave plate 133G, the polarizationbeam splitter 134G, and the half-wave plate 135G, the color combiningprism 136, and the polarization plate 137 of the components of the firstimage generator 100 are shown in the figure.

Moreover, a reflective polarizer 231R, a reflective optical modulator232G, a wave plate 233G, a polarization beam splitter 234G, a half-waveplate 235G, a color combining prism 236, and a polarization plate 237 ofthe components of the second image generator 200 are shown in thefigure.

FIGS. 3 and 4 are enlarged diagrams each showing a portion of the imagecombining unit 50 in an enlarged state. In FIG. 3 , behaviors of thefirst image light beam 10 emitted from the first image generator 100 areschematically shown. In FIG. 4 , behaviors of the second image lightbeam 20 emitted via the half-wave plate 60 from the second imagegenerator 200 are schematically shown.

As shown in FIG. 3 , most of a first image light beam 10A which is theP-polarized light beam emitted from the first image generator 100 passthrough the junction surface 51 and travel toward the projection opticalsystem 70. The optical path of the first image light beam 10A thatenters the junction surface 51 in this X direction and a first imagelight beam 10B that passes through the junction surface 51 and travelstoward the projection optical system 70 also in the X direction is amain optical path OP1.

The main optical path OP1 is the optical path of the image light beam(modulated light beam) until the projection optical system 70 projectsthe image light beam (modulated light beam) to the screen or the likeafter the image light beam (modulated light beam) is generated.Therefore, the image combining unit 50 is disposed on the main opticalpath OP1 of the image light beam (modulated light beam).

On the other hand, the first image light beams 10 emitted from the firstimage generator 100 also includes a first image light beam 10C reflectedto the front (in the figure, downwards) in the Y direction by thejunction surface 51. The first image light beam 10C becomes so-calledleaking light and travels along another optical path OP2 different fromthe main optical path OP1.

In this embodiment, the image combining unit 50 functions as an opticaldevice that splits the first image light beam 10A emitted from the firstimage generator 100 into the first image light beam 10B and the firstimage light beam 10C, which each travel in a different direction. Thatis, the image combining unit 50 is disposed on the main optical path OP1of the first image light beam 10, emits the first image light beam 10Balong the main optical path OP1, and emits the first image light beam10C along the other optical path OP2.

The junction surface 51 of the image combining unit 50 functions as alight-splitting surface disposed obliquely to the direction of incidence(X direction) of the first image light beam 10 that enters the imagecombining unit 50. Specifically, a surface of the junction surface 51that the first image light beam 10 enters corresponds to alight-splitting surface.

In this embodiment, the junction surface 51 (light-splitting surface) isdisposed at an angle of 45 degrees with respect to the direction ofincidence (X direction) of the first image light beam 10. The junctionsurface 51 transmits the first image light beam 10B which is a part ofthe first image light beam 10A that enters the junction surface 51 andreflects the first image light beam 10C which is another part of thefirst image light beam 10A.

The projection optical system 70 projects the first image light beam 10Bwhich travels toward the projection optical system 70 to the screen orthe like. In this case, a part of the first image light beam 10B can bereflected by the projection lens or the like in the projection opticalsystem 70.

The reflected light beam reflected by the projection lens or the likebackwardly travels on the main optical path OP1 which is the opticalpath of the first image light beam 10B and enters the junction surface51 again. The reflected light beam that enters the junction surface 51again is transmitted toward the first image generator 100 or isreflected toward the second image generator 200. In either case, it doesnot travel along the other optical path OP2 which is the optical path ofthe first image light beam 10C.

That is, the image combining unit 50 and the junction surface 51 alsohave a function of preventing the reflected light beam, which backwardlytravels on the main optical path OP1 and enters the image combining unit50 and the junction surface 51, from travelling along the other opticalpath OP2. In this embodiment, the first image light beam 10B correspondsto a first split light beam and the first image light beam 10Ccorresponds to a second split light beam. Further, the main optical pathOP1 corresponds to a first optical path and the other optical path OP2corresponds to a second optical path.

Moreover, the color combining prism 136 of the first image generator 100corresponds to a combining unit that combines a plurality of modulatedlight beams and generates a combined modulated light beam (first imagelight beam 10). Further, the projection optical system 70 corresponds toa projecting unit that projects the combined modulated light beamcombined by a color-combining unit. The image combining unit 50 isdisposed between the color combining prism 136 and the projectionoptical system 70 and splits the combined modulated light beam (firstimage light beam 10A) into the first image light beam 10B and the firstimage light beam 10C.

As shown in FIG. 3 , the sensor unit 80 (sensor 81) is disposed on theother optical path OP2 which is the optical path of the first imagelight beam 10C and detects a state of the first image light beam 10C.The junction surface 51 of the image combining unit 50 prevents thereflected light beam from the projection optical system 70 fromtravelling along the other optical path OP2. Therefore, the reflectedlight beam from the projection optical system 70 does not enter thesensor 81 and it is possible to sufficiently suppress generation ofnoise components due to the reflected light beam. Accordingly, a stateof the first image light beam 10C can be detected with high accuracy anda state of the first image light beam 10A emitted from the first imagegenerator 100 can be detected with high accuracy.

It can be said that the position at which the sensor 81 is disposed is aposition on a side of the light-splitting surface that reflects thefirst image light beam 10C to travel along the other optical path OP2.In a case where the sensor 81 is disposed on a side of thelight-splitting surface on a side which the first image light beam 10Aenters, the reflected light beam, which enters a surface on an oppositeside of the light-splitting surface (on a side of the surface on whichthe first image light beam 10B is emitted), can be prevented fromtravelling along the other optical path OP2.

In this embodiment, the image combining unit 50 is configured in such amanner that two right-angled isosceles prisms of substantially the sametype are joined. Such a prism-type configuration is a configurationincluded in the light-splitting prism according to the presenttechnology.

As shown in FIG. 3 , four side surfaces parallel to the Z direction ofthe image combining unit 50 are first to fourth side surfaces 52 a to 52d.

The first side surface 52 a is a surface which is disposed facing thefirst image generator 100. The first image light beam 10 is madeincident upon that surface. The second side surface 52 b is a surfacewhich is disposed facing the second image generator 200. The secondimage light beam 20 is made incident upon that surface. The third sidesurface 52 c is a surface to which the first image light beam 10B isemitted along the main optical path OP1. The fourth side surface 52 d isa surface to which the first image light beam 10C is emitted along theother optical path OP2.

The sensor 81 is disposed on a side of the fourth side surface 52 d towhich the first image light beam 10C is emitted. Specifically, thesensor 81 is disposed in proximity to the fourth side surface 52 d. Thesensor 81 may be held in contact with the fourth side surface 52 d ormay be spaced apart from the fourth side surface 52 d.

By employing a configuration of a prism type as the image combining unit50, it becomes easy to attach the sensor 81. In this embodiment, thefirst side surface 52 a corresponds to a first surface. The fourth sidesurface 52 d corresponds to a second surface and a second emittingsurface. The third side surface 52 c corresponds to a first emittingsurface.

Moreover, most of the first image light beam 10A that enters thejunction surface 51 travel along the main optical path OP1 as the firstimage light beam 10B. Then, the first image light beam 10C which isother part travels along the other optical path OP2. That is, thejunction surface 51 of the image combining unit 50 splits the firstimage light beams 10B and 10C such that the amount of light of the firstimage light beam 10B is larger than the amount of light of the firstimage light beam 10C. Accordingly, it is possible to sense the firstimage light beam 10 while sufficiently reducing the loss of the amountof light of the to image to be projected. It should be noted that theleaking light is utilized as an object to be sensed, and thus the lossof the amount of light is little even in comparison with theconventional one.

As shown in FIG. 4 , most of the second image light beam 20 which is theS-polarized light beam emitted from the second image generator 200 viathe half-wave plate 60 are is reflected by the junction surface 51 andtravels toward the projection optical system 70. Optical paths of asecond image light beam 20A that enters the junction surface 51 in thisY direction and a second image light beam 20B which is reflected by thejunction surface 51 in the X direction and travels toward the projectionoptical system 70 become the main optical path OP1.

In this embodiment, the optical path of the second image light beam 20Bis substantially identical to the optical path of the first image lightbeam 10B shown in FIG. 3 . Therefore, at the stages subsequent to thejunction surface 51, the first image light beam 10B and the second imagelight beam 20B travel along the same main optical path OP1.

On the other hand, the second image light beam 20 emitted from thesecond image generator 200 also includes a second image light beam 20Cwhich passes through the junction surface 51 in the Y direction. Thesecond image light beam 20C becomes a so-called leaking light beam andtravels along the other optical path OP2 different from the main opticalpath OP1.

In this embodiment, the optical path of the second image light beam 20Cis substantially identical to the optical path of the first image lightbeam 10C shown in FIG. 3 . Therefore, the first image light beam 10C andthe second image light beam 20C travel along the same other optical pathOP2.

The image combining unit 50 functions as an optical device that splitsthe second image light beam 20A emitted from the second image generator200 into the second image light beam 20B and the second image light beam20C, which each travel in a different direction. That is, the imagecombining unit 50 is disposed on the main optical path OP1 of the secondimage light beam 20, emits the second image light beam 20B along themain optical path OP1, and emits the second image light beam 20B alongthe other optical path OP2.

The junction surface 51 of the image combining unit 50 also functions asa light-splitting surface disposed obliquely to the direction ofincidence (Y direction) of the second image light beam 20 that entersthe image combining unit 50. Specifically, a surface of the junctionsurface 51 that the second image light beam 20 enters corresponds to thelight-splitting surface. That is, the light-splitting surface withrespect to the first image light beam 10 and the light-splitting surfacewith respect to the second image light beam 20 are the surfaces oppositeto each other.

In this embodiment, the junction surface 51 (light-splitting surface) isdisposed at an angle of 45 degrees with respect to the direction ofincidence (Y direction) of the second image light beam 20. The junctionsurface 51 reflects the first image light beam 20B which is a part ofthe second image light beam 20A that enters the junction surface 51 andreflects the second image light beam 20C which is another part of thesecond image light beam 20A.

Moreover, the image combining unit 50 and the junction surface 51prevent the reflected light beam, which backwardly travels on the mainoptical path OP1 and enters the image combining unit 50 and the junctionsurface 51, from travelling along the other optical path OP2. That is,also regarding the second image light beam 20, the reflected light beamreflected by the projection optical system 70 is prevented fromtravelling along the other optical path OP2. It should be noted that thesecond image light beam 20B corresponds to the first split light beamand the second image light beam 20C corresponds to the second splitlight beam. Further, the main optical path. OP1 corresponds to the firstoptical path and the other optical path OP2 corresponds to the secondoptical path.

Moreover, a color combining prism 236 of the second image generator 200corresponds to the combining unit that combines a plurality of modulatedlight beams to generate a combined modulated light beam (second imagelight beam 20). The image combining unit 50 is disposed between thecolor combining prism 236 and the projection optical system 70 andsplits the combined modulated light beam (second image light beam 20A)into the second image light beam 10B and the second image light beam10C.

As shown in FIG. 4 , the sensor unit 80 (sensor 81) is disposed on theother optical path OP2 which is the optical path of the second imagelight beam 20C and detects a state of the second image light beam 10C.The junction surface 51 of the image combining unit 50 prevents thereflected light beam from the projection optical system 70 fromtravelling along the other optical path OP2. Therefore, the reflectedlight beam from the projection optical system 70 does not enter thesensor 81 and generation of noise components due to the reflected lightbeam can be sufficiently suppressed. Accordingly, the second image lightbeam 20C can be detected with high accuracy and the second image lightbeam 20A emitted from the second image generator 200 can be detectedwith high accuracy.

That is, in this embodiment, with respect to the junction surface 51 ofthe image combining unit 50, the sensor 81 is disposed on the otheroptical path OP2 configured to be on a side opposite to the main opticalpath OP1. Accordingly, the first image light beam 10 in theP-polarization state and the second image light beam 20 in theS-polarization state can be respectively sensed with high accuracy.

Note that it can be said that the position at which the sensor 81 isdisposed is a surface on a side on which the second image light beam 20Cis emitted along the other optical path OP2, i.e., a position on a sideof a surface on an opposite side of the light-splitting surface. In acase where the sensor 81 is arranged on the side of the surface on anopposite side of the light-splitting surface, the reflected light beam,which enters the light-splitting surface on a side on which the secondimage light beam 20B is reflected, can be prevented from travellingalong the other optical path OP2.

As in FIG. 3 , four side surfaces parallel to the Z direction of theimage combining unit 50 are the first to fourth side surfaces 52 a to 52d. The sensor 81 is disposed on the side of the fourth side surface 52 dto which the second image light beam 20C is emitted. Specifically, thesensor 81 is disposed in proximity to the fourth side surface 52 d. Inthis embodiment, the second side surface 52 b corresponds to the firstsurface. The fourth side surface 52 d corresponds to the second surfaceand the second emitting surface. The third side surface 52 c correspondsto the first emitting surface.

Moreover, most of the second image light beam 20A that enters thejunction surface 51 are reflected as the second image light beam 20B andtravel along the main optical path OP1. Then, the second image lightbeam 20C which is the other part passes along the other optical pathOP2. That is, the junction surface 51 of the image combining unit 50splits the second image light beams 20B and 20C such that the amount oflight of the second image light beam 20B is larger than the amount oflight of the second image light beam 20C. Accordingly, the second imagelight beam 20 can be sensed while sufficiently suppressing the loss ofthe amount of light of the image to be projected. It should be notedthat the leaking light is utilized as an object to be sensed, and thusthe loss of the amount of light is little even in comparison with theconventional one.

FIGS. 5 and 6 are schematic diagrams each showing a configurationexample of the sensor unit 80. The sensor unit 80 illustrated in FIGS. 5and 6 includes a circuit hoard 83 connected to a flexible circuit board82 and the sensor 81 mounted on the circuit board 83. A signal of lightintensity measured by the sensor 81 is output to the control unit 90 orthe like in FIG. 1 via the circuit board 83 and the flexible circuitboard 82. Further, the sensor 81 and the circuit board 83 are suppliedwith a control signal and driving power.

The sensor 81 includes a light-receiving surface 84 and a part of thelight-receiving surface 84 is set as a measurement area 85 (ActiveArea). FIG. 6 is a schematic diagram showing the measurement area 85 ofthe sensor 81. The sensor 81 includes a plurality of measurement units86 capable of measuring intensity of an incident light beam. That is,the plurality of measurement units 86 is arranged in the measurementarea 85. The plurality of measurement units 86 is arranged in atwo-dimensional form in directions orthogonal to each other. In thisembodiment, a total of 40 measurement units 86 of 4 (horizontal) by 10(vertical) are arranged in a matrix form.

Moreover, the sensor 81 includes a plurality of filters 87 each disposedat each of the plurality of measurement units 86. The plurality offilters 87 transmits light beams in a predetermined wavelength range.That is, the filters 87 are arranged corresponding to the 40 measurementunits 86, respectively. In this embodiment, the plurality of filters 87includes, as three types of filters, a red filter 87R that transmitslight in the red wavelength range, a green filter 87G that transmitslight in the green wavelength range, and a blue filter 87B thattransmits light in the blue wavelength range.

When the first and second image light beams 10C and 20C are madeincident upon the measurement area 85, the measurement unit 86 in whichthe red filter 87R is disposed measures intensity of the modulated redlight beam R. Similarly, the measurement unit 86 in which the greenfilter 87G is disposed measures intensity of the modulated green lightbeam G. The measurement unit 86 in which the blue filter 87B is disposedmeasures intensity of the modulated blue light beam B. For example, amean value of intensity measured by the plurality of measurement units86 in which the filters 87 for the same color are disposed is used.

As shown in FIG. 6 , the plurality of filters 87 is disposed such that afilter group 88 arranged in the x direction includes three types offilters 87R, 87G, and 87B of red, green, and blue. Further, theplurality of filters 87 is disposed such that the filters 87 of the samekind among the three types of filters 87R, 87G, and 87B are not adjacentin the second direction. Accordingly, the three types of filters 87R,87G, and 87B can be uniformly arranged in the measurement area 85. As aresult, modulated light intensity of the respective RGB colors can beaccurately measured. It should be noted that the arrangement method ofthe three types of filters 87R, 87G, and 87B are not limited to the oneshown in FIG. 6 and may be set as appropriate.

Moreover, in this embodiment, the plurality of filters 87 includes noisefilters 87N. The noise filters 87N transmit light of noise components,which are respectively transmitted by the three types of filters 87R,87G, and 87B of red, green, and blue. That is, the noise to filters 87Ntransmit light of noise components passing through the red filter 87R,light of noise components passing through the green filter 87G, andlight of noise components passing through the blue filter 87B.

The noise filters 87N detect light in a wavelength range of about 200 nmto about 660 nm at low sensitivity of about 1 to 5%. Therefore, themeasurement unit 86 (hereinafter, referred to as a noise measurementunit) in which the noise filters 87N are disposed is capable ofmeasuring light intensity detected as light of noise components by themeasurement units 86 of the respective colors. The intensity of light ofnoise components, which is measured by the noise measurement units 86,is subtracted from the respective RGB light intensity, which has beenmeasured by the measurement units 86R, 86G, and 86B of the respectivecolors. In this manner, the modulated light intensity of the respectivecolors can be measured with high accuracy.

As shown in FIG. 6 , the noise filters 87N are disposed such that atleast one of them is included in the filter group 88 arranged in thehorizontal direction. Further, the noise filters 87N are disposed not tobe adjacent in the vertical direction. Accordingly, the noise filters87N can be uniformly arranged in the measurement area 85, and themodulated light intensity of the respective RGB colors can be accuratelymeasured.

It should be noted that in this embodiment, noise components resultingin the reflected light beam from the projection optical system 70 aresufficiently reduced. Therefore, a more accurate image can be projectedeven without using the noise filters 87N. As a matter of course, muchmore accurate image may be projected by using the noise filters 87N.

In this embodiment, when a measurement mode of the first and secondimage light beams 10 and 20 is selected, the control unit 90 shown inFIG. 1 switches between emission of the first image light beam 10 by thefirst image generator 100 and emission of the second image light beam 20by the second image generator 200 as appropriate for performing it.

For example, in a state in which the emission operation by the secondimage generator 200 is turned off, the first image generator 100 emitsan image light beam for measurement (a concept included in the firstimage light beam 10). The image light beam for measurement is an imagelight beam for projecting a white image, a black image, and anotherarbitrary image, for example. It should be noted that the operation ofprojecting an image light beam also includes an operation of preventingprojection of an image light beam in a case of displaying a black imageor the like. Further, an image light beam of an content to image or thelike to be an object to be viewed may be emitted. The sensor unit 80detects a state of the image light beam for measurement and thedetection result is output to the control unit 90.

After that, in the state in which the emission operation of the firstimage generator 100 is turned off, the second image generator 200 emitsan image for measurement (a concept included in the second image lightbeam 20). The sensor unit 80 detects a state of the image formeasurement and the detection result is output to the control unit 90.

The timing for selecting the measurement mode is not limited. Forexample, the measurement mode may be automatically selected inaccordance with the timing at which the user activates the image displayapparatus 500 or the timing at which an instruction to terminate drivingof the image display apparatus 500 is input. For example, there can be acase of performing measurement in accordance with a timing at which alogo mark of a maker or the like at the time of activation is displayed,a case of displaying a black screen on a stand-by mode until thetermination of driving is completed and performing measurement, and thelike. As a matter of course, the user may input an instruction toperform measurement and select the measurement mode in accordance withthat input instruction.

The control unit 90 detects the luminance (intensity), the chromaticity,and the luminous flux shape, and the like of the first and second imagelight beams 10 and 20 on the basis of a state of the image light beamfor measurement emitted from each of the first and second imagegenerators 100 and 200. That is, in this embodiment, the control unit 90also functions as a part of the sensor unit 80.

For example, calibration is performed on the basis of the state of theimage light beam for measurement of each of them. The calibrationenables measurement and correction of white balance (white chromaticity)and measurement and correction of a color space, i.e., measurement andcorrection of single color chromaticity of RGB to be performed with highaccuracy, for example. Further, various types of processing such asmeasurement and correction of gamma can be performed. For example, in acase where the image display apparatus 500 includes a luminance sensorthat adjusts the luminance of an image in accordance with surroundingbrightness, correction and the like of the luminance adjustment functionby that luminance sensor can also be performed.

Moreover, balance of the luminance, chromaticity, and the like of theright-eye image and the left-surface image can also be adjusted. Otherprocessing and the like based on the detection result of the sensor unit80 will be described later with effects of the image display apparatus500 according to this embodiment.

FIG. 7 is a schematic view showing another configuration example of thesensor unit 80. The sensor unit 80 shown in FIG. 7 includes a firstpolarization plate 89 a that transmits a light beam to become aP-polarized light beam with respect to the junction surface 51 of theimage combining unit 50 and prevents light beams in other polarizationstates from travelling through the first polarization plate 89 a, and afirst sensor 81 a that detects the light beam in the P-polarizationstate that passes through the first polarization plate 89 a.

Moreover, the sensor unit 80 includes a second polarization plate 89 bthat transmits a light beam to become an S-polarized light beam withrespect to the junction surface 51 of the image combining unit 50 andprevents light beams in other polarization states from travellingthrough the second polarization plate 89 b, and a second sensor 81 bthat detects the light beam in the S-polarization state that passesthrough the second polarization plate 89 b.

The first image light beam 10C emitted from the first image generator100 enters the first sensor 81 a via the first polarization plate 89 a.The second image light beam 20C emitted from the second image generator200 enters the second sensor 81 b via the second polarization plate 89b. Therefore, in the sensor unit 80 shown in FIG. 7 , the states of thefirst and second image light beams 10 and 20 can be detected at the sametime without switching the emission operation of each of the first andsecond image generators 100 and 200.

Accordingly, for example, without setting the measurement mode, thestates of the first and second image light beams 10 and 20 can beconstantly detected also in projection of the content image or the like.As a result, a very highly accurate image can be projected by constantlyfeeding back detection results.

In the example shown in FIG. 7 , the first polarization plate 89 acorresponds to a first filter that extracts the light beam in the firstpolarization state and the second polarization plate 89 b corresponds toa second filter that extracts a light beam in the second polarizationstate. As a matter of course, other optical components other than thewave plate may be used.

As still another configuration example, one sensor may be arranged and apolarization device such as a polarization plate may be rotatablyarranged in front thereof. Control of the rotational angle of thepolarization device as appropriate enables the first and second imagelight beams 10 and 20 to be switched as appropriate to enter the sensor.Output of the result detected by the sensor and the rotational angle ofthe polarization device to the control unit 90 in association with eachother enables whether the detection result relates to the first imagelight beam 10 or the second image light beam 20 to be easily determined.Even with this configuration, the states of the first and second imagelight beams 10 and 20 can be constantly detected also in projection ofthe content image or the like without setting the measurement mode.

FIG. 8 is a schematic diagram showing a configuration example of animage display apparatus 900 shown as a comparative example. In the imagedisplay apparatus 900 as the comparative example, sensors 981 (981R,981G, and 981B) are disposed in vicinity of reflective polarizers 931(931R, 931G, and 931B) (prism-type beam splitters) for the respectiveRGB colors, which are included in a first image generator 901.

Specifically, the sensors 981 are disposed in proximity to surfaces ofthe reflective polarizers 931, which are opposite to surfaces which therespective RGB light beams enter. The sensors 981 for the respective RGBcolors detect states of leaking light of the respective color lightbeams that has not been reflected by the reflective polarizers 931 andhas passed through the reflective polarizers 931.

Hereinafter, effects exerted by the image display apparatus 500according to this embodiment will be described as compared to theconfiguration of the image display apparatus 900 shown in FIG. 8 .

Sensing Accuracy

As shown in FIG. 8 , in the image display apparatus 900, reflected lightbeams 905 reflected by a projection optical system 970 backwardly travelon the main optical path of the first and second image light beams 10and 20 and enter the reflective polarizers 931. Then, the reflectivepolarizers 931 reflect the reflected light beams 905 toward the sensors981 and the reflected light beams 905 enter the sensors 981. That is, inthe image display apparatus 900, interface reflection of projected lightbeams (image light beams) at the projection lens or the like directlyenters the sensors 981, and thus noise components significantlyincrease. As a result, the sensing accuracy of the sensors 981 issignificantly lowered.

In contrast, in the image display apparatus 500 according to thisembodiment, the reflected light beam from the projection optical system70 does not enter the sensor 81 and generation of noise components dueto the reflected light beam can be sufficiently suppressed. Accordingly,high sensing accuracy can be achieved.

Correlation with Projected Light Beam

In the image display apparatus 900 shown in FIG. 8 , only light beamsbefore they are modulated by reflective optical modulators 932 can besensed. That is, light beams different from image light beams projectedby the projection optical system 70 are sensed at a positionsignificantly spaced apart from the projection optical system 70.Therefore, the sensing accuracy consequently lowers by sensing lightbeams having low correlation with projected light beams (image lightbeams).

In contrast, in the image display apparatus 500 according to thisembodiment, the sensor unit 80 is disposed in vicinity of the imagecombining unit 50 disposed just in front of the projection opticalsystem 70. Then, the first and second image light beams 10 and 20generated by the first and second image generators 100 and 200 aresensed. Therefore, light beams having high correlation with projectedlight beams (image light beams) projected by is the projection opticalsystem 70 can be sensed and high sensing accuracy can be achieved.Further, very high sensing accuracy can be achieved even in comparisonwith a case of sensing a diffracted light beam or the like of projectedlight beams.

Degradation Detection of Optical Members

In the image display apparatus 900 shown in FIG. 8 , light beams beforethey enter the reflective optical modulators 932 are sensed. Therefore,degradation of optical members included in an image modulating unit 930such as the reflective optical modulators 932 cannot be detected on thebasis of the sensing result.

In contrast, in the image display apparatus 500 according to thisembodiment, the first and second image light beams 10 and 20 emittedfrom the first and second image generators 100 and 200 are sensed. Thatis, light beams passing through the reflective polarizers 131, thereflective optical modulators 132, the wave plates 133, the polarizationbeam splitters 134, the half-wave plates 135, the color combining prism136, and the polarization plate 137 included in the image modulatingunit 130 illustrated in FIG. 2 are sensed.

Therefore, degradation of those optical components can be detected onthe basis of the sensing result of the sensor unit 80. As a matter ofcourse, degradation and the like of an adhesive to be used for coatingformed on the optical components, adhesion of the optical components,and the like can also be detected. For example, on the basis of adetection result such as black level degradation and lowering of thewhite luminance, degradation of the reflective optical modulators 132,the wave plates 133 that functions as compensation plates, thepolarization beam splitters 134 that adjusts the polarization state, orthe like can be detected as appropriate.

As a result, for example, an optical component can be replaced at asuitable timing, and the maintenance cost and the like can be reduced.Further, a new optical component for replacement can be prepared asappropriate before the optical component is completely broken, forexample. That is, the repairing period can be reduced by preparing acomponent for replacement in advance for expected failure.

Adjustment of Compensation Plate by Feed-Back of Black Luminance

The image display apparatus 500 according to this embodiment can also beprovided with a mechanism capable of rotating the shafts of the waveplates 133 that functions as the compensation plates through a motor andthe like. In this case, the shafts of the wave plates 133 can be rotatedby feed-back of the black luminance detected by the sensor unit 80.Accordingly, contrast degradation due to deviation of the compensationplates can be prevented. Alternatively, lowering of the contrast causedby degradation of the other optical members can also be compensated. Theadjustment of the compensation plates may be automatically performed ormay be performed in accordance with a user's operation via a remotecontroller or the like.

The positions, angles, and the like of the other optical components maybe changed on the basis of the sensing result of the sensor unit 80. Byconstituting an adjustment mechanism and the like inside the imagedisplay apparatus 500 as appropriate, high-accuracy image display basedon the sensing result can be performed.

Sensing of Prism

The emission operation of each of the first and second image generators100 and 200 is switched or the sensor unit 80 shown in FIG. 7 isconstituted. Accordingly, the white luminance of the color combiningprisms 136 and 236 included in the first and second image generators 100and 200, respectively can be measured. High-accuracy image display canbe achieved by controlling the operation of the light source section 101or the like, for example, on the basis of a measurement result of thewhite luminance.

Number of Sensors

In the image display apparatus 900 shown in FIG. 8 , sensors for therespective RGB colors are required for each of the first and secondimage generators. That is, a total of six sensors are required and thecomponent cost increases. In the image display apparatus 500 accordingto this embodiment, one or two sensors is capable of detecting a stateof each of the first and second image light beams 10 and 20, and thusthe component cost can be reduced.

Moving Mechanism Is Unnecessary

In the image display apparatus 900 shown in FIG. 8 , it is conceivablethat the sensor is moved as appropriate on an optical path between animage combining unit 950 and the projection optical system 970 forsensing the first and second image light beams. That is, it is aconfiguration in which the sensor is moved on the optical path forsensing and the sensor is moved outside the optical path during normaloperation.

In this case, a moving mechanism that moves the sensor is required,which makes the apparatus complicated. Further, a space for insertingthe sensor is required, which increases the size of the apparatus. Forexample, in a case where the distance from the first and second imagegenerators to the image combining unit 950 increases, the back focusincreases. It contributes to an increase in size of the projectionoptical system and design is also difficult. Moreover, there is apossibility that moving the sensor causes lowering of the reliability ofthe sensing result, an increase in operation time, an increase in thecost, and the like.

In the image display apparatus 500 according to this embodiment, suchproblems do not arise because the sensor unit 80 is fixed on the backside of the image combining unit 50.

Other Embodiments

The present technology is not limited to the above-mentioned embodimentand various other embodiments can be made.

FIGS. 9 to 11 are schematic diagrams each showing another configurationexample of the image generator. As shown in FIG. 9 , the prism-type beamsplitters may be replaced by other polarization devices such as wiregrid polarizers as reflective polarizers 631 (631R, 631G, and 631B).Further, orientations in which reflective optical modulators 632 (632R,632G, and 632B) are disposed are also not limited and may be set asappropriate. As in the above-mentioned embodiment, the states of thefirst and second image light beams can be detected with high accuracy byarranging a sensor unit 680 on the back side of an image combining unit650 positioned just in front of a projection optical system 670.

As shown in FIG. 10 , transmissive optical modulators 732 (732R, 732G,and 732B) may be used. For example, polarization plates and compensationplates are disposed, sandwiching the transmissive optical modulators 732therebetween. Alternatively, an arbitrary configuration may be employed.As in the above-mentioned embodiment, states of the first and secondimage light beams can be detected with high accuracy by arranging asensor unit 780 on the back side of an image combining unit 750positioned just in front of a projection optical system 770.

FIG. 11 is a schematic diagram showing a configuration example of animage display apparatus including a single image generator. That is,rather than generating and combining a plurality of images such as aright-eye image and a left eye image, a single image generated by asingle image generator 801 is projected via a projection optical system870.

In the image generator 801 shown in FIG. 11 , a green modulated lightbeam G modulated by a reflective optical modulator 832G enters a colorcombining prism 836. A red modulated light beam R modulated by areflective optical modulator 832R and a modulated light beam B of bluemodulated by a reflective optical modulator 832B are emitted along thesame optical path as a reflective polarizer 831RB and enter the colorcombining prism 836.

The color combining prism 836 functions as an embodiment of an opticaldevice according to the present technology. That is, the color combiningprism 836 reflects a part of the green modulated light beam G toward theprojection optical system 870 as the first split light beam. The colorcombining prism 836 transmits another part of the green modulated lightbeam G as it is as the second split light beam.

Moreover, the color combining prism 836 transmits a part of the redmodulated light beam R and a part of the blue modulated light beam B asthey are toward the projection optical system 870 as the first splitlight beam. The color combining prism 836 reflects another part of thered modulated light beam R and another part of the blue modulated lightbeam B as the second split light beam to travel on an optical path ofthe other part of the green modulated light beam G.

A sensor unit 880 is disposed on optical paths of the other parts of therespective RGB colors (second split light beam). The color combiningprism 836 prevents the reflected light beam from the projection opticalsystem 870 from entering the sensor unit 880. Therefore, a state of eachof the modulated light beams of RGB can be detected with high accuracy.

As described above, the present technology is not limited to the imagedisplay apparatus that generates two images by using the six opticalmodulators and combining them and is applicable to an arbitrary imagedisplay apparatus. For example, the image generator as illustrated inFIG. 2, 9 , or 10 can also be disposed alone and the prism-type beamsplitter disposed as the image combining unit can also be disposed asthe optical device according to the present technology. For example,instead of the polarization plate 137 shown in FIG. 2 , a prism-typepolarization beam splitter like the image combining unit 50 is disposedas the optical component that adjusts the polarization state. Then, astate of an image light beam emitted from the image generator can bedetected with high accuracy by arranging the sensor unit on the backside thereof.

Moreover, the optical device according to the present technology can bedisposed at an arbitrary position on the main optical path. For example,the polarization beam splitters 134 shown in FIG. 2 may be used as anembodiment of the optical device according to the present technology andthe sensor unit may be disposed on the back side thereof. Also in thiscase, a state of the image light beam can be detected with highaccuracy.

Regarding the optical device according to the present technology, it isnot limited to the polarization beam splitter and a half mirror, a glassplate, or the like can be used. An arbitrary optical component capableof splitting the light beam into the first and second split light beamsand prevents the light beam, which backwardly travels on the opticalpath of the first split light beam, from travelling along the opticalpath of the second split light beam may be used. In a case where aplate-like optical component, not the prism type, is used, a surface ona side on which the first split light beam is emitted becomes the firstemitting surface and a surface on which the second split light beam isemitted becomes the second emitting surface.

Moreover, an angle of the light-splitting surface that crosses theincident light beam is also not limited to 45 degrees and may bearbitrarily set.

The present technology is not limited to the case where the first andsecond image light beams are image light beams of the right-eye imageand the left eye image in the image display apparatus using the sixliquid-crystal panels and the like. The same image light beams generatedon the basis of the same image signals may be respectively projected asthe first and second image light beams. For example, the lifetime of theliquid-crystal panel and the like can be prolonged by reducing theamount of light of the light beams that enter the liquid-crystal paneland the like. Then, combining and projecting the same images cansuppress lowering of the luminance and high luminance is achieved. As amatter of course, an interesting viewing effect can also be provided byvoluntarily combining and projecting different images.

Hereinabove, the case of sensing leaking light of each of the first andsecond image light beams has been exemplified. That is, the opticalcomponent configured for applying a predetermined action to the incidentlight beam splits the incident light beam into a first split light beamto which the predetermined action is applied and a second split lightbeam to which the predetermined action is not applied. For example, withthe above-mentioned image combining unit, the application of thepredetermined action is transmission/reflection with respect to thepredetermined polarization states. Then, the first split light beam towhich the transmission/reflection action with respect to thepredetermined polarization states are applied and the second split lightbeam to which this action is not applied are split.

The present technology is not limited. The first and second split lightbeams may be emitted by applying the predetermined action to both. Forexample, it is the case where the half mirror exemplified above is usedor the like.

At least two features of the above-mentioned features according to thepresent technology can also be combined. That is, various featuresdescribed in the respective embodiments may be arbitrarily combinedacross the respective embodiments. Further, the above-mentioned variouseffects are merely exemplary and not limitative. Moreover, other effectsmay be provided.

It should be noted that, the present technology can also take thefollowing configurations.

(1) An image display apparatus, including:

an optical modulator;

an optical device that

-   -   splits a modulated light beam modulated by the optical modulator        into a first split light beam and a second split light beam, the        first split light beam and the second split light beam each        travelling in a different direction, and    -   prevents a light beam, which backwardly travels on an optical        path of the first split light beam and enters the optical        device, from travelling along an optical path of the second        split light beam; and

a sensor unit that is disposed on the optical path of the second splitlight beam and detects a state of the second split light beam.

(2) The image display apparatus according to (1), in which

the optical device

-   -   is disposed on a main optical path of the modulated light beam,    -   emits the first split light beam along the main optical path,        and    -   emits the second split light beam along another optical path,        and

the sensor unit is disposed on the other optical path.

(3) The image display apparatus according to (1) or (2), in which

the optical device includes

-   -   a first emitting surface that emits the first split light beam,        and    -   a second emitting surface that emits a second split light beam,        the second emitting surface being different from the first        emitting surface, and

the sensor unit is disposed on a side of the second emitting surface.

(4) The image display apparatus according to any one of (1) to (3), inwhich

the optical device includes a light-splitting surface that is disposedobliquely to a direction of incidence of the modulated light beam thatenters the optical device.

(5) The image display apparatus according to (4), in which

the light-splitting surface

-   -   transmits a part of the modulated light beam that enters the        light-splitting to surface as the first split light beam, and    -   reflects another part of the modulated light beam as the second        split light beam, and

the sensor unit is disposed on a side of the light-splitting surfacethat reflects the second split light beam.

(6) The image display apparatus according to (4), in which

the light-splitting surface

-   -   reflects a part of the modulated light beam that enters the        light-splitting surface as the first split light beam, and    -   transmits another part of the modulated light beam as the second        split light beam, and

the sensor unit is disposed on a side of a surface on an opposite sideof the light-splitting surface.

(7) The image display apparatus according to any one of (1) to (6), inwhich

the optical device splits the modulated light beam such that an amountof light of the first split light beam is larger than an amount of lightof the second split light beam.

(8) The image display apparatus according to any one of (1) to (7),further including:

a combining unit that combines a plurality of modulated light beams togenerate a combined modulated light beam and

a projecting unit that projects the combined modulated light beamgenerated by the combining unit, in which

the optical device

-   -   is disposed between the combining unit and the projecting unit,        and    -   splits the combined modulated light beam into the first split        light beam and the second split light beam.        (9) The image display apparatus according to any one of (1) to        (8), in which

the optical device includes a light-splitting prism including

-   -   a first surface that the modulated light beam enters,    -   a light-splitting surface that splits the modulated light beam        that enters the first surface, and    -   a second surface from which the second split light beam split by        the light-splitting surface is emitted, and

the sensor unit is disposed in proximity to the second surface of thelight-splitting prism.

(10) The image display apparatus according to any one of (1) to (9), inwhich

the optical device includes a polarization beam splitter, a half mirror,or a glass plate.

(11) The image display apparatus according to any one of (1) to (10),further including

a first emitter that emits a first image light beam in a firstpolarization state in a first direction, in which

the optical device includes a light-splitting surface that is disposedobliquely to the first direction,

the light-splitting surface

-   -   transmits a part of the first image light beam to travel on a        first optical path extending in the first direction, and    -   reflects another part of the first image light beam to travel on        a second optical path extending in a second direction        substantially orthogonal to the first direction, and

the sensor unit is disposed on the second optical path.

(12) The image display apparatus according to (11), further including

a second emitter that emits a second image light beam in a secondpolarization state in the second direction, in which

the light-splitting surface

-   -   is disposed obliquely to the second direction,    -   reflects a part of the second image light beam to travel on the        first optical path, and    -   transmits another part of the second image light beam to travel        on the second optical path.        (13) The image display apparatus according to (12), in which

the sensor unit includes

-   -   a first filter that extracts a light beam in the first        polarization state,    -   a first sensor that detects a state of the light beam extracted        by the first filter,    -   a second filter that extracts a light beam in the second        polarization state, and    -   a second sensor that detects a state of the light beam extracted        by the second filter.        (14) The image display apparatus according to any one of (1) to        (13), in which

the sensor unit detects at least one of intensity, chromaticity, or aluminous flux shape of the second split light beam.

(15) The image display apparatus according to any one of (1) to (14), inwhich

the optical device

-   -   is configured for applying a predetermined action to an incident        light beam, and    -   splits the modulated light beam that enters the optical device        into the first split light beam to which the predetermined        action is applied and the second split light beam to which the        predetermined action is not applied.

REFERENCE SIGNS LIST

-   OP1 main optical path-   OP2 another optical path-   10, 10A, 10B, 10C first image light beam-   20, 20A, 20B, 20C second image light beam-   50, 650, 750 image combining unit-   51 junction surface-   70, 670, 770, 870 projection optical system-   80, 680, 780, 880 sensor unit-   81 sensor-   81 a first sensor-   81 b second sensor-   89 a first polarization plate-   89 b second polarization plate-   100 first image generator-   110 illumination optical system-   130 image modulating unit-   132 (132R, 132G, and 132B), 232G, 632, 832R, 832G, 832B reflective    optical modulator-   200 second image generator-   500 image display apparatus-   732 transmissive optical modulator-   801 image generator-   836 color combining prism

The invention claimed is:
 1. An image display apparatus, comprising: afirst optical device configured to extract a light beam corresponding toa first color, the first color being one of red, green, and blue, asecond optical device configured to split the light beam into a firstsplit light beam and a second split light beam, the first split lightbeam and the second split light beam each travelling in a differentdirection, and a sensor disposed on an optical path of the second splitlight beam and comprising a first filter and a second filter, the sensorbeing configured to detect a state of the second split light beam,wherein the first filter is configured to transmit a light beam in afirst wavelength range corresponding to the first color, the secondfilter is configured to transmit a light beam in a second wavelengthrange, the second wavelength range being broader than the firstwavelength range, and the sensor is configured to detect a state of eachof a light beam passing through the first filter and a light beampassing through the second filter, wherein the sensor includes aplurality of the first filters and a plurality of the second filters,and each of the plurality of the second filters is arranged to not benext to another one of the second filters.
 2. The image displayapparatus according to claim 1, wherein the second optical device is ahalf mirror device.
 3. The image display apparatus according to claim 1,wherein the sensor is configured to detect an intensity of the secondsplit light beam by detecting the intensity of the light beam passingthrough the first filter and the light beam passing through the secondfilter.
 4. The image display apparatus according to claim 1, wherein thefirst optical device is configured to split a light beam correspondingto white into the extracted light beam, which corresponds to red as thefirst color, and into a light beam corresponding to green and blue basedon wavelength.
 5. The image display apparatus according to claim 4,further comprising a third optical device configured to split the lightbeam corresponding to green and blue into a light beam corresponding togreen and a light beam corresponding to blue based on wavelength.
 6. Theimage display apparatus according to claim 1, wherein the sensor furthercomprises a third filter configured to transmit a light beam in a thirdwavelength range corresponding to one of green or blue.
 7. The imagedisplay apparatus according to claim 6, wherein the sensor furthercomprises a fourth filter configured to transmit a light beam in afourth wavelength range corresponding to the other one of green or blue.8. The image display apparatus according to claim 7, wherein the firstcolor corresponds to red.
 9. The image display apparatus according toclaim 1, wherein the second filter is configured to transmit a noisecomponent in the light beam passing through the first filter.
 10. Theimage display apparatus according to claim 1, further comprising anoptical modulation device configured to modulate the light beamextracted by the first optical device, wherein the second optical deviceis configured to split the light beam modulated by the opticalmodulation device into the first split light beam and the second splitlight beam.
 11. An image display method, comprising: extracting, by afirst optical device, a light beam corresponding to a first color, thefirst color being one of red, green, and blue, splitting, by a secondoptical device, the light beam into a first split light beam and asecond split light beam, the first split light beam and the second splitlight beam each travelling in a different direction, and detecting astate of the second split light beam by a sensor disposed on an opticalpath of the second split light beam, the sensor comprising a firstfilter and a second filter, wherein the first filter is configured totransmit a light beam in a first wavelength range corresponding to thefirst color, the second filter is configured to transmit a light beam ina second wavelength range, the second wavelength range being broaderthan the first wavelength range, and the detecting includes detecting astate of each of a light beam passing through the first filter and alight beam passing through the second filter, wherein the sensorincludes a plurality of the first filters and a plurality of the secondfilters, and each of the plurality of the second filters is arranged tonot be next to another one of the second filters.
 12. The image displaymethod according to claim 11, wherein the second optical device is ahalf mirror device.
 13. The image display method according to claim 11,further comprising: detecting, by the sensor, an intensity of the secondsplit light beam by detecting the intensity of the light beam passingthrough the first filter and the light beam passing through the secondfilter.
 14. The image display method according to claim 11, furthercomprising: splitting, by the first optical device, a light beamcorresponding to white into the extracted light beam, which correspondsto red as the first color, and into a light beam corresponding to greenand blue based on wavelength.
 15. The image display method according toclaim 14, further comprising: splitting, by a third optical device, thelight beam corresponding to green and blue into a light beamcorresponding to green and a light beam corresponding to blue based onwavelength.
 16. The image display method according to claim 11, whereinthe sensor further comprises a third filter configured to transmit alight beam in a third wavelength range corresponding to one of green orblue.
 17. The image display method according to claim 16, wherein thesensor further comprises a fourth filter configured to transmit a lightbeam in a fourth wavelength range corresponding to the other one ofgreen or blue.
 18. The image display method according to claim 11,wherein the first color corresponds to red.
 19. The image display methodaccording to claim 11, wherein the second filter is configured totransmit a noise component in the light beam passing through the firstfilter.
 20. The image display method according to claim 11, furthercomprising modulating, by an optical modulation device, the light beamextracted by the first optical device, wherein the second optical deviceis configured to split the light beam modulated by the opticalmodulation device into the first split light beam and the second splitlight beam.